In general, in an image forming apparatus such as a digital copying machine that handles image information, reading means such as a scanner reads an original. Image information read and digitized is multi-valued, processed according to a purpose, and outputted from an output apparatus such as a laser printer.
An image forming apparatus such as a color multifunction peripheral that forms a color image has a specific image discriminating function. The specific image discriminating function discriminates whether a read original is a specific original such as a bill or a marketable security. When an input image is the specific original, an output apparatus prohibits copying of the input image by, for example, entirely painting the image in black (JP-A-2005-184497).